I’ve been having some interesting discussions with my friends over at NetApp recently. I wanted to learn more about their new clustered Data ONTAP 8.2 features and its new scale-out functionality. In the storage array world, traditional scale-up mechanisms usually involved either replacing disk drives with faster/newer models or replacing old array controllers with newer controllers. In worst case scenarios, fork lift upgrades are required to do a technology refresh of your array. Another approach, scale-out, is fast becoming the accepted way of handling storage requirements going forward. Scale out storage is now big news. With scale-out, you simply add additional resources to your already existing shared storage pool.
Over the past year I have been to a number of VMUGs (VMware User Group) meetings and have sat in on some of the NetApp sessions on their clustered Data ONTAP release. NetApp have also realized that the demand is there for scale-out, and they have introduced their very own unified scale-out storage solution called clustered Data ONTAP. Basically, this allows you to take a bunch of different NetApp storage array models and cluster them together to provide a single, unified and virtualized share storage pool. Using clustered Data ONTAP 8.2, NetApp customers can now increase scalability using a scale-out rather than a scale-up approach. Let’s look at clustered Data ONTAP and some of the new features it brings in more detail. Continue reading →
Last year, NetApp announced a new host side cache accelerator feature to compliment their Virtual Storage Tiering (VST) technology. Rather than keeping all your data in flash, VST places hot data in flash while moving cold data to cheaper and slower media. NetApp are offering this as an end-to-end technology, from server to array controller (Flash Cache) to disk pools (Flash Pools). One of the major parts of this is Flash Accel, which was also announced in the latter part of last year, and is the server-side flash component of VST. On the back of their recently announced All Flash Array, NetApp are also making Flash Accel available to the general public.
I just received notification about KB article 2016122 which VMware has just published. It deals with a topic that I’ve seen discussed recently on the community forums. The symptom is that during periods of high I/O, NFS datastores from NetApp arrays become unavailable for a short period of time, before becoming available once again. This seems to be primarily observed when the NFS datastores are presented to ESXi 5.x hosts.
The KB article described a work-around for the issue which is to tune the queue depth size on the ESXi hosts which will reduce I/O congestion to the datastore. By default, the value of NFS.MaxQueueDepth is 4294967295 (which basically means unlimited). The workaround is to change this value to 64. This has been shown to prevent the disconnects. A permanent solution is still being investigated.
I recommend all NetApp customers read this KB article, whether you have been impacted or not.